I'm a third year undergrad in a public university in Texas. Because of a personal situation, I'm currently unable to attend most lectures (lately none) of a particular math class. However, I have a friend in my section who keeps me updated with the material covered, homework assignments, and exam dates.
I had previously spoken to the professor, explaining that I might be missing sessions throughout the semester, and she seemed understanding; lately, however, I stopped going altogether, and I've exclusively shown up for mid-term examinations (on which I do ok). To my surprise, I've been able to teach myself quite well, and, given that it saves me a considerable amount of time, I've been thinking of adopting this practice in the future.
So: my question is: assuming that attendance isn't compulsory, is it reasonable for students to skip a large numbers of lectures? Will most instructors take this personally? Would there be other unanticipated consequences?